Conveyors: power-driven – Conveyor section – Endless conveyor
Reexamination Certificate
2002-02-22
2004-05-11
Hess, Douglas (Department: 3651)
Conveyors: power-driven
Conveyor section
Endless conveyor
C198S851000, C198S852000, C198S853000
Reexamination Certificate
active
06732856
ABSTRACT:
TECHNICAL FIELD
The present invention is directed to a modular conveyor belt, and more particularly, to a modular conveyor belt including a plurality of modular links which are assembled without the use of welding or transverse connectors.
BACKGROUND OF THE INVENTION
Wire conveyor belts serve important functions in industry because of their durability and versatility in performing a wide variety of functions under differing conditions. However, wire grid conveyor belts require widthwise-extending rods to interconnect wire lengths which have been bent to form a plurality of links, as shown for example in U.S. Pat. No. 5,622,252, and woven metal wire belts require interweaving and welding wherein widthwise-extending rods are used to interconnect wire lengths which have been wound into spirals, as set forth for example in U.S. Pat. No. 4,491,003. Generally, metal wire belts must be assembled at the belt manufacturer's site to a user's specifications. Also, welding and other steps, in assembly of the wire spirals and connecter rods, are carried out manually.
In order to overcome some of the manufacturing complications encountered with metal wire belts, plastic and ceramic conveyor belts utilizing modules with inter-fitting link ends have become well known and well worked. Generally, in such belts, a pivot rod connects the interfitting link ends so that the modules can be assembled with the rods to form a continuous belt. The rods permit angular rotation between adjacent modules as required when the belt goes around sprockets or rolls on the conveyors while at the same time the rods connect and transmit the forces between the adjacent modules. In practice these connecting rods are subject to large forces. Due to the broad range of application in which plastic conveyors are commonly used, the forces and the reaction of the rods to these forces is many times unpredictable. It is of utmost importance that the rods that connect the modules be positively captured within the conveyor belt assembly. Failure to accomplish such results in numerous problems, not the least of which is the belt actually falling apart in use. Other problems include interference between partially exposed rods and the surrounding conveyor structure. Additionally, as a practical matter the rods must be easily insertable and removable from the belt, as such is normally required during belt assembly, belt installation or belt repair. Furthermore, it is desirable to accomplish this without the use of any special equipment or tool. Such is particularly important when considering field installation and repair since special tools represent both added costs and inconvenience to the user.
Because of the significant problems that loose conveyor rods have caused, numerous methods have been used to capture the pivot rods connecting the links in plastic conveyor belts. Such methods include forming “button” heads on the ends of the rods, but these button heads can be knocked off and they must be removed for replacement of the rods. The button heads have generally been formed by melting the ends of the rod to provide enlarged ends or button heads which are larger in diameter than the rod hole and thereby prevent the rod from moving inwardly through the belt, i.e., the enlarged heads provides means to capture the rods. However, there are numerous problems with this solution to the problem of capturing the rods. First, special equipment is normally required to thermally form the heads. Secondly, the button heads are exposed on the edges of the belt in a vulnerable location since any protuberance on a conveyor can either wear or knock the heads of the rods thus allowing the rods to fall out of the belt. Thirdly, there is the problem of dimensional instability which leads to Poisson effect, i.e., when a material undergoes a change in dimension due to an elastic deformation along one axis, an opposite change in dimension or deformation occurs along a perpendicular axis. The amount of this opposite deformation is determined by Poisson's ratio. When the conveyor belt is in operation the rods are subjected to compressive forces perpendicular to the axis of the rod. These compressive forces can deform the rod making the diameter of the rod smaller in accordance with the theory of elasticity. In accordance with the Poisson effect the rod then elongates along its axis; in effect, the rod becomes longer than its original length. This in turn causes the rod to protrude further beyond the edge of the belt causing further problems of interference with conveyor structure which can result in significant belt damage and possible down time.
Another way of capturing the rod within the belt is to form a circumferential bead the internal diameter of which is less than the diameter of the rod, the beads being formed at the ends of the rod holes. Such is shown in U.S. Pat. No. 2,911,091, for example. However, such capturing of the rod is more or less permanent which doesn't take into consideration the need for disassembly and repair of the belt from time to time. Another solution to the problem of capturing a rod end is disclosed in U.S. Pat. No. 3,726,569, in which the end of the rod hole and the outermost link end are plugged to prevent the rod from escaping from the belt. U.S. Pat. No. 4,709,807, also discloses a similar arrangement. However, such plugs can be inadequate due to the rod elongation force caused by Poisson's effect mentioned above and threaded plugs can cause stress risers and possible failure, in addition to extra manufacturing time and the cost of threading both the plug and the hole.
Another known method of capturing the rod is a snap-fitting end cap installed axially into the module rod hole or transversely into the module blocking off the rod hole. However, the general design requirement for snap-fit assembly as currently known requires that the plug or end cap be flexible so that its snap projection can deform during installation. This flexibility, which is normally accomplished by placing the snap-fit projection at the ends of two flexible arms, also weakens the plug or cap and reduces its ability to resist rod elongation forces. Further, end caps which are installed axially into the rod hole place the entire rod elongation force caused by the Poisson effect on relatively small snap-fit projections. This results in the rods “popping” the end caps off of the end modules.
There is thus a need in the art for an improved modular conveyor belt which overcomes the disadvantages heretofor encountered when inter-linking modules to form a conveyor belt.
SUMMARY OF THE INVENTION
The present invention overcomes these disadvantages by providing a modular conveyor belt assembly having a plurality of modular links, each of the modular links including at least one pair of first projecting legs and at least one pair of second projecting legs, the first projecting legs each having an inwardly projecting engagement element and the second projecting legs each having an engagement slot. The plurality of modular links are interconnected to form a conveyor belt through engagement of the engagement elements in the engagement slots.
A further aspect of the present invention provides a modular conveyor belt assembly including a plurality of modular links, each of the modular links having substantially planar opposing sides, at least one pair of first projecting legs, and at least one pair of second projecting legs. The first projecting legs each have a projecting engagement element and the second projecting legs each have an engagement slot. The plurality of modular links are interconnected to form the conveyor belt, a first one of the engagement elements of a first one of the plurality of modular links cooperating with the engagement slot of a second one of the plurality of modular links and a second one of the engagement element of the first one of the plurality of modular links cooperating with the engagement slot of a third one of the plurality of modular links.
REFERENCES:
patent: 3066549 (1962-12-01), Benjamin
patent:
Hess Douglas
Maryland Wire Belts, Inc.
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